The present invention relates to a valve-lash adjuster equipped valve operating device for an internal combustion engine, and particularly to techniques for improving operating characteristics of a hydraulic zero-valve-lash adjuster employed in an engine valve operating device, capable of providing zero valve clearance (or zero valve lash) when restarting the engine.
One such zero valve-lash adjuster equipped valve operating device has been disclosed in Japanese Patent Provisional Publication No. 2000-213313 (hereinafter is referred to as JP2000-213313). In the valve operating device disclosed in JP2000-213313, a hydraulic zero lash adjuster is installed in an electromagnetically-operated valve. The valve operating unit of JP2000-213313 includes a flange-shaped or disk-shaped armature and an armature shaft, both constructing a flanged plunger, a pair of electromagnetic coils respectively facing to both faces of the flange-shaped armature, and a pair of coil springs permanently biasing an intake valve stem respectively in a direction opening the intake valve and in a direction closing the intake valve, the coil spring pair cooperating with the electromagnetic coil pair to electromagnetically open and close the intake valve by electromagnetic force (attraction force) plus spring bias. The hydraulic zero lash adjuster is disposed between the intake-valve stem end and the armature shaft end, to provide zero valve lash and to provide a cushioning effect that permits this arrangement without undue shock loading and thus to reduce noise during operation. The hydraulic lash adjuster is designed to axially slightly contract, while leaking working oil from a high-pressure chamber in a state where the intake valve is opening. On the contrary, when the intake valve becomes conditioned in its fully-closed state, the hydraulic lash adjuster axially expands by supplying working oil into the high-pressure chamber as the clearance between the intake-valve stem end and the armature shaft end increases. A compressive force (or a spring load) axially acts on the hydraulic zero lash adjuster by means of the lower spring, which biases the intake-valve stem in the valve-closing direction. Oil leak from the high-pressure chamber to the reservoir chamber is restricted by means of a check valve built in the zero lash adjuster, thus maintaining the axial length of the zero lash adjuster. Actually, there is a possibility of leakage of oil from the aperture defined between component parts of the zero lash adjuster. In the stopped state of the engine, the zero lash adjuster is axially spring-loaded between the armature shaft and the intake-valve stem end in the compressive direction. Due to the spring load, the working fluid in the high-pressure chamber is compressed, and whereby a portion of working fluid tends to leak from the high-pressure chamber. With the lapse of time, there is an increased tendency for the zero lash adjuster to remarkably contract owing to the spring load. When restarting the engine with such remarkable contraction of the zero lash adjuster, the zero lash adjuster tends to axially rapidly expand, and thus air is introduced into each of the reservoir chamber and the high-pressure chamber and undesirably blended with the working fluid in these chambers. This results in unstable opening and closing operations of the intake valve. In particular, when a working-fluid chamber of a zero lash adjuster has a relatively small volumetric capacity, the accuracy of opening and closing operations of the intake valve may be greatly affected by working fluid mixed with air.
Accordingly, it is an object of the invention to provide a valve-lash adjuster equipped valve operating device, which avoids the aforementioned disadvantages.
In order to accomplish the aforementioned and other objects of the present invention, a valve operating device for an internal combustion engine with an engine valve that opens and closes either of an intake port and an exhaust port of the engine, comprises a biasing device that biases the engine valve in a valve-closing direction, a valve drive mechanism that opens the engine valve against a biasing force of the biasing device, a hydraulic zero lash adjuster disposed between the engine valve and the valve drive mechanism to adjust each of a clearance between the hydraulic zero lash adjuster and the engine valve and a clearance between the hydraulic zero lash adjuster and the valve drive mechanism to a zero clearance, and a restriction device that restricts a compressive force applied from each of the engine valve and the valve drive mechanism to the hydraulic zero lash adjuster when the engine is stopped.
According to another aspect of the invention, a valve operating device for an internal combustion engine with an engine valve that opens and closes either of an intake port and an exhaust port of the engine, comprises a biasing device that biases the engine valve in a valve-closing direction, a valve drive mechanism that opens the engine valve against a biasing force of the biasing device, a hydraulic zero lash adjuster disposed between the engine valve and the valve drive mechanism to adjust each of a clearance between the hydraulic zero lash adjuster and the engine valve and a clearance between the hydraulic zero lash adjuster and the valve drive mechanism to a zero clearance, a restriction device that restricts a compressive force applied from each of the engine valve and the valve drive mechanism to the hydraulic zero lash adjuster when the engine is stopped, the valve drive mechanism comprising (a) a drive shaft rotating in synchronism with rotation of an engine crankshaft and having a drive cam integrally formed on an outer periphery of the drive shaft, (b) a rockable cam opening the engine valve against a biasing force produced by the biasing device via the hydraulic zero lash adjuster, (c) a rocker arm linked at one end to the drive cam and linked at the other end to the rockable cam, and (d) a control shaft having a control cam integrally formed on an outer periphery of the control shaft and oscillatingly supporting the rocker arm via the control cam, the valve lift of the engine valve being variably controlled by adjusting an angular position of the control shaft based on engine operating conditions and by changing a center of oscillating motion of the rocker arm, and the valve lift being set to the zero lift by controlling the angular position of the control shaft by means of the restriction device.
According to a further aspect of the invention, a valve operating device for an internal combustion engine with an engine valve that opens and closes either of an intake port and an exhaust port of the engine, comprises a biasing device that biases the engine valve in a valve-closing direction, a valve drive mechanism that opens the engine valve against a biasing force of the biasing device, a hydraulic zero lash adjuster disposed between the engine valve and the valve drive mechanism to adjust each of a clearance between the hydraulic zero lash adjuster and the engine valve and a clearance between the hydraulic zero lash adjuster and the valve drive mechanism to a zero clearance, a restriction device that restricts a compressive force applied from each of the engine valve and the valve drive mechanism to the hydraulic zero lash adjuster when the engine is stopped, the valve drive mechanism comprising (a) an armature mechanically linked to the engine valve (b) a valve-opening electromagnet creating an attraction force acting on the armature in a direction opening of the engine valve, (c) a valve-closing electromagnet creating an attraction force acting on the armature in a direction closing of the engine valve, and (d) a biasing device creating a biasing force that holds the engine valve toward a neutral position by biasing the engine valve in the direction opening of the engine valve and in the direction closing of the engine valve, the hydraulic zero lash adjuster being disposed between the engine valve and the armature, and the restriction device comprising a restriction member that restricts movement of the armature toward the hydraulic zero lash adjuster and movement of the engine valve toward the hydraulic zero lash adjuster when the engine is stopped.
According to a still further aspect of the invention, a valve operating device for an internal combustion engine with an engine valve that opens and closes either of an intake port and an exhaust port of the engine, comprises a biasing means for biasing the engine valve in a valve-closing direction, a valve drive means for opening the engine valve against a biasing force of the biasing means, a valve-lash adjusting means disposed between the engine valve and the valve drive means for adjusting each of a clearance between the valve-lash adjusting means and the engine valve and a clearance between the valve-lash adjusting means and the valve drive means to a zero clearance, and a restriction means for restricting a compressive force applied from each of the engine valve and the valve drive means to the valve-lash adjusting means when the engine is stopped.
According to another aspect of the invention, a valve operating device for an internal combustion engine with an engine valve that opens and closes either of an intake port and an exhaust port of the engine, comprises a biasing device that biases the engine valve in a valve-closing direction, a valve drive mechanism that opens the engine valve against a biasing force of the biasing device, a hydraulic zero lash adjuster disposed between the engine valve and the valve drive mechanism to adjust each of a clearance between the hydraulic zero lash adjuster and the engine valve and a clearance between the hydraulic zero lash adjuster and the valve drive mechanism to a zero clearance, a restriction device that restricts a compressive force applied from each of the engine valve and the valve drive mechanism to the hydraulic zero lash adjuster when the engine is stopped, a cam that changes rotary motion of the cam to reciprocating motion of the engine valve, and the restriction device returning the valve lift to the zero lift so that there is no application of the compressive force from each of the engine valve and the valve drive mechanism to the hydraulic zero lash adjuster when the engine is stopped.
According to another aspect of the invention, a valve operating device for an internal combustion engine with an engine valve that opens and closes either of an intake port and an exhaust port of the engine, comprises a biasing device that biases the engine valve in a valve-closing direction, a valve drive mechanism that opens the engine valve against a biasing force of the biasing device, a hydraulic zero lash adjuster disposed between a stem end of the engine valve and the valve drive mechanism to adjust each of a clearance between the hydraulic zero lash adjuster and the engine valve and a clearance between the hydraulic zero lash adjuster and the valve drive mechanism to a zero clearance, a restriction device that restricts a compressive force applied from each of the engine valve and the valve drive mechanism to the hydraulic zero lash adjuster when the engine is stopped, the valve drive mechanism comprising (a) an armature mechanically linked to the engine valve, (b) a valve-opening electromagnet creating an attraction force acting on the armature in a direction opening of the engine valve, (c) a valve-closing electromagnet creating an attraction force acting on the armature in a direction closing of the engine valve, (d) a biasing device creating a biasing force that holds the engine valve toward a neutral position by biasing the engine valve in the direction opening of the engine valve and in the direction closing of the engine valve, and (e) an armature shaft to which the hydraulic zero lash adjuster is linked; the armature shaft being concentric to a stem of the engine valve, and the restriction device comprising a restriction member that locks the armature shaft so that there is no application of the compressive force from each of the engine valve and the valve drive mechanism to the hydraulic zero lash adjuster when the engine is stopped.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.